U.S. patent number 3,646,606 [Application Number 04/847,946] was granted by the patent office on 1972-02-29 for physiological monitoring system.
This patent grant is currently assigned to Care Electronics, Inc.. Invention is credited to Richard L. Buxton, George N. Miller.
United States Patent |
3,646,606 |
Buxton , et al. |
February 29, 1972 |
PHYSIOLOGICAL MONITORING SYSTEM
Abstract
A physiological monitoring system for hospitalized patients
wherein each of the patients monitored would be provided a patient
monitoring unit which would electrically sense two or more
physiological conditions, translate desired information into
digital form and transmit it by pulse coded FM radio link to a
central monitoring station. The central monitoring station would
receive transmitted information from one or more patients so
equipped and detect and display the information in analog and
digital form and in some instances provide automatic alarms on the
occurrence of certain predetermined values for the sensed
conditions.
Inventors: |
Buxton; Richard L. (Huntsville,
AL), Miller; George N. (Huntsville, AL) |
Assignee: |
Care Electronics, Inc.
(N/A)
|
Family
ID: |
25301911 |
Appl.
No.: |
04/847,946 |
Filed: |
August 6, 1969 |
Current U.S.
Class: |
600/483;
128/903 |
Current CPC
Class: |
A61B
5/0006 (20130101); A61B 5/02455 (20130101); Y10S
128/903 (20130101) |
Current International
Class: |
A61B
5/00 (20060101); A61B 5/0245 (20060101); A61B
5/024 (20060101); A61b 005/04 () |
Field of
Search: |
;128/2R,2.5M,2.5A,2.6R,2.1A,2.1R |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Geddes et al. "American Journal of Medical Electronics" Jan-Mar.
1962, pp. 62-69. .
Kahn et al. "American Journal of Medical Electronics," Apr.-Jan.
1963, pp. 152-157..
|
Primary Examiner: Kamm; William E.
Claims
What is claimed as our invention is:
1. A physiological monitoring system for remotely monitoring a
plurality of physiological conditions of at least one hospitalized
patient comprising:
A. at least one patient unit for sensing a plurality of
physiological conditions and providing electrical signals
representative thereof, each said circuit including at least one
heart sensor, at least one blood pressure sensor, and at least one
temperature sensor and further including:
1. commutation means having an input channel for each sensed
condition and being responsive to said signals for providing a
serial output consisting of repeated sequential samplings of said
signals,
2. signal conditioning means responsive to the output of and
operating in synchronization with said commutation means for
selectively adjusting the reference level of the now serially
arranged signals,
3. analog-to-digital translation means responsive to said signal
conditioning means for providing a digitally encoded word signal
for each sample of a given physiological signal and for providing a
signal indicating the completion of single word and the completion
of a set of words; and
4. radio transmission means for transmitting said encoded word
signals by a pulse-code, frequency-modulated radio frequency
carrier;
B. a central monitor for indicating physiological conditions from
at least one said patient unit and including:
1. receiving means including a radio receiver for each patient unit
for receiving a radio signal from a said patient unit,
2. digital-to-analog conversion means responsive to an output from
each said receiver for providing analog outputs including at least
one heart responsive signal and at least one blood pressure
responsive signal,
3. cathode-ray tube means for selectively displaying at least one
heart responsive signal and at least one blood pressure responsive
signal from each patient monitored,
4. heart rate means responsive to a said heart responsive signal of
a patient for indicating the rate of heart beat of that
patient,
5. preshock detection means responsive to the amplitude of a said
heart responsive signal for indicating the presence of overvoltage
signals and a preshock condition,
6. systolic detection and indicating means responsive to a blood
pressure signal output of said digital-to-analog converter for
detecting and indicating maximum values of blood pressure,
7. diastolic detection and indicating means responsive to a blood
pressure signal output of said digital-to-analog converter for
detecting and indicating minimum values of blood pressure,
8. binary to binary coded decimal conversion means responsive to a
selected said receiving means for providing a first plurality of
outputs wherein at least one output is a decimally coded
temperature signal, and for providing a second plurality of outputs
wherein at least one output is a signal marking the period of
accurate readout of blood pressure signal and at least one said
output is a signal marking the period of accurate readout of a said
temperature signal,
9. decimally indicated systolic blood pressure indicating means
comprising:
a. first systolic gating means responsive to the coincidence of an
output from said systolic detection means marking the period of
occurrence of a systolic condition and said output from said binary
to binary coded decimal conversion means marking the period of
accurate readout of a said blood pressure signal for providing a
systolic occurrence gating signal,
b. systolic decimal readout means,
c. second systolic gating means responsive to an output of said
first systolic gating means and a said decimally coded blood
pressure signal from said binary to binary coded decimal conversion
means for providing a systolic blood pressure digitally encoded
signal to said systolic decimal readout means,
10. decimally indicated diastolic blood pressure indicating means
comprising:
a. first diastolic gating means responsive to the coincidence of an
output from said diastolic detection means marking the period of
occurrence of a diastolic condition and a said output from said
binary to binary coded decimal conversion means marking the period
of accurate readout of a said blood pressure signal for providing a
diastolic occurrence gating signal,
b. diastolic decimal readout means,
c. second diastolic gating means responsive to an output of said
first diastolic gating means and a said decimally coded blood
pressure signal from said binary to binary coded decimal conversion
means for providing a diastolic blood pressure digitally encoded
signal to said diastolic decimal readout means,
11. at least one digital temperature readout means, and
12. gating means responsive to a said decimally coded temperature
signal and a signal marking the period of accurate readout of said
temperature signal for providing a digitally coded signal to said
digital temperature readout means.
2. A physiological monitoring system as set forth in claim 1
wherein at least one said blood pressure sensor requires an applied
operating bias and said system further comprises means for
providing said operating bias only during the periods in which the
output of said blood pressure sensor is being passed through said
commutating means.
3. A physiological monitoring system as set forth in claim 1
wherein said central monitor further comprises recording means for
selectively recording at least one said signal.
Description
This invention relates to measurement systems and particularly to a
system for the measurement and display of physiological
conditions.
Equipment for the measurement of physiological conditions by
electrical sensing means has been developed to the point where
extremely valuable measurements can be obtained of such things as,
for example, cardiac condition, blood pressure and temperature.
However, a number of problems exist with respect to existing
apparatus, particularly in the area of interface between
measurement equipment and the medical observer who must, with a
high degree of efficiency, extract measured data and act on it. A
further problem area lies in presently used means for communicating
data between the person of the patient and the data readout
equipment.
Accordingly, it is a primary object of this invention to bridge the
gap between the art of raw measurement of physiological conditions
and the normal abilities and frailities of persons charged with the
responsibility of continuously monitoring the physiological
conditions of a patient or, in most cases, several patients, and to
provide an overall system wherein the critical interface between a
patient's condition and the monitoring doctor or nurse is much more
effectively and efficiently achieved than heretofore.
It is a further object of this invention to provide for centralized
or remote monitoring of conditions of a number of patients without
the necessity of wire linkage between the patients and the
monitoring equipment; thus, freeing patients to move about without
restraint and making unnecessary the substantial wiring that would
be normally necessary to construct such a monitoring system.
It is a further object of this invention to provide a system of
intensive care monitoring which does not require particular
location of patients.
It is still a further object of this invention to provide the
necessary communications link between a patient and central
monitoring equipment by radio means capable of dependable operation
in a hospital environment.
It is still another object of this invention to provide a patient
measurement unit which may be operated with very low power
consumption permitting relatively long periods of operation without
the necessity of replacing battery power sources.
It is a still further object of this invention to provide for
accurate data resolution by means of the use of a particular form
of digitally encoded data.
In accordance with the invention, a plurality of patients, for
example, eight patients, requiring intensive care are each equipped
with a measurement unit which electrically measures several
physiological conditions pertinent to the ailment of the patient,
for example, heart condition, blood pressure and temperature.
Electrical outputs from body probes providing these measurements
are fed through preamplifiers to a commutator which provides a
single continuous output signal made up of repeated, serially
arranged, samplings of the individual sensed conditions. Next a
signal conditioner, operating in synchronization with the
commutator, selectively adjusts, as needed, the reference level of
the now serially occurring physiological signals. After this, each
physiological signal is translated into a digitally encoded word,
which together with appropriate synchronization information, is
transmitted by a pulse-coded modulated FM transmitter to a central
monitor. The central monitor receives transmissions on separate
frequency channels from each patient unit and translates the
transmitted data variously to achieve accurate and optimumly
presented reproductions of sensed physiological conditions. For
example, heart and blood pressure data is translated into analog
form and indicated by meter and cathode-ray display. Blood pressure
and temperature data is translated into decimal form and directly
presented as decimal quantities on digital displays. In addition,
an E.C.G. signal is analyzed for overvoltage output and a preshock
state indicated by a warning signal. Similarly, systolic and
diastolic (high and low) arterial blood pressure excursions are
detected and a warning signal given if there is a departure from
preset values. Diastolic and systolic blood pressure values are
also presented in decimal form by gating a decimal readout, to
display and hold high and low blood pressure values.
These and other objects, features and advantages of the invention
will be readily appreciated from the following description when
considered together with the accompanying drawings in which:
FIG. 1 is a schematic illustration of the overall system of the
invention;
FIG. 2 is an electrical schematic circuit diagram of a patient worn
unit of this invention;
FIG. 3 is an electrical schematic circuit diagram of the central
monitoring unit of this invention; and
FIG. 4 is a view along the lines 4--4 of FIG. 3 illustrating the
cathode-ray tube presentation provided by the circuit of FIG.
2.
FIG. 1 generally illustrates the system of the invention as applied
to an intensive care application in which eight patients are
monitored by a single medical observer. Each patient is equipped
with a patient measurement unit 10, designated P1- P8. The patients
may be in separate rooms, making unnecessary a special location for
patients requiring intensive care. Central monitoring unit 12 is
functionally divided, in general, into Receiver Section 14, "Every
Patient Continuous Monitoring" (EPCM) section 16, "Patient
Selective Monitoring" (PSM), section 18 and Cathode-Ray Display
(CRD), section 20. In the "Every Patient Continuous Monitoring"
section there is continuous monitoring of systolic blood pressure,
heart rate and continuous monitoring for preshock indications.
There is also selectable continuous monitoring of any one of
several conditions.
FIG. 2 generally illustrates the circuit arrangement of patient
unit 10. ECG, electrocardogram, electrodes 22, 24 and 26 together
with ground or reference electrode 28 are appropriately positioned
in contact with a patient and function to pick up electrical
potentials or signals generated by the heart. These signals,
labeled A, B and C, respectively, are amplified in preamplifiers
30, 32 and 34, respectively, and applied to separate channels of
eight channel multiplexer 36.
Arterial and veinal blood pressure transducers 38 and 40 sense
blood pressure and provide through preamplifiers 42 and 44 blood
pressure signals labeled D and E to separate channel inputs of
multiplexer 36.
Temperature of a patient is typically sensed by both a skin
temperature probe 46 and internal temperature probe 48 in
conjunction with bridge networks 50 and 52, respectively, and the
resulting signal outputs fed as inputs G and H to separate channels
of multiplexer 36. As an auxiliary or reserve function channel, any
appropriate transducer 54 may be employed together with any
appropriate signal conditioning device 56 and applied as an
auxiliary input F to multiplexer 36. For simplicity of designation,
the channels of multiplexer 36 are also referred to as A-H in
accordance with the signal designations.
Multiplexer 36 functions to sample each of the input channels
sequentially at a rate which provides for each channel to be
sampled for a period of 250 microseconds permitting sampling of all
eight channels in a period of 2,000 microseconds, a sampling rate
of 500 times per second. Multiplexer 36 is driven or controlled by
gating pulses generated by sync generator and logic control 58 of
analog-to-digital converter 60. The time shared outputs of
multiplexer 36 are in differential signal form and are fed to
signal conditioner 62. The function of signal conditioner 62 is to
properly scale the various types of signal information applied to
it for analog-to-digital conversion. For example, the three ECG
signals are referenced at 21/2 volts, that is with no signal
provided by transducers 22, 24 or 26, the conditioned signals have
a value of 21/2 volts. The same reference is applied to the
auxiliary or multipurpose open channel F. The blood pressure
channels are referenced at 0, that is with a 0 input on blood
pressure channels F and E, the output of signal conditioner 62 is
also zero. Similarly, the temperature channels G and H are
referenced with respect to 0 and no biasing, or addition of bias is
effected. Conditioning is achieved by applying from reference level
circuit 64 to signal conditioner 62 a reference voltage of 21/2
volts, or other appropriate level, during and only during the
required periods, that is during the periods channels A-C and F are
being passed by multiplexer 36. At other times the reference
voltage is held at zero. Reference level circuit 64 is controlled
by an appropriate train of control pulses from sync generator and
logic control 58 of analog-to-digital converter 60 to accomplish
synchronized application of reference voltages.
The output of signal conditioner 62 is fed to analog-to-digital
converter 60 which converts the Pulse Amplitude Modulated (PAM)
output of signal conditioner 62 to digital form, having for
example, a maximum scale output of 5.1 volts. A 10-bit digital word
system is used in which the first eight bits are representative of
the converted analog information and the last two bits accomplish
word and frame identification, respectively. The duration of a bit
determines the presence or absence of a coded or weighted digit,
with a bit of 6 microsecond duration representing a "0" and a bit
of 18 microseconds representing a "1." The end of a word is marked
by a 12 microsecond pulse in the ninth bit position and the
presence of a 12 microsecond pulse in both the ninth and 10th bit
positions mark the end of a frame. A word corresponds to one
sampling of the amplitude of one of the physiological conditions
being sampled and a frame correspond to one complete set of words
or set of samplings of the physiological conditions being
monitored.
The output of analog-to-digital converter 60 is applied to and
pulse code modulates FM transmitter 66. The presence of a 6
microsecond pulse shifts the carrier about 100 kHz., a 12
microsecond pulse shifts it about 100 kHz. and a 18 microsecond
pulse shifts the carrier about 100 kHz. Typically, the carrier
frequency of a transmitter 66 would be in the FM broadcast range of
88 to 108 MHz. By the use of pulse code width modulation, extremely
accurate and dependable intrahospital communications are achieved
despite the presence of substantial radiation from other equipment
such as X-ray and diathermy machines.
Blood pressure transducers 38 and 40 typically require an operating
bias current of approximately 10 ma. each and as a feature of this
invention the operating bias is keyed on only during the periods
when channels D and E are gated open by keying pulses d.sub.p and
e.sub.p, respectively, from multiplexer 36 by switching means
integral with probe, or probe assemblies 38 and 40. Thus operating
power is applied to each of transducers 38 and 40 for one-eighth of
the time normally required, thus significantly reducing the overall
operating power requirements for a patient unit. In fact, the
reduction is approximately 40 percent.
FIG. 3 shows the circuit arrangement of central monitor 12. As
stated above, it is basically divided between Radio Receiving
Section 14, "Every Patient Continuous Monitoring" Section 16,
"Patients Selective Section" 18 and Cathode-Ray Display 20. Radio
receiving section 14 consists of eight radio receivers, each tuned
to the frequency channel of a like designated patient unit (FIG.
1). It has been determined that clear FM broadcast channels (for
the particular locale) provide excellent communication channels
with very low power. Each "Every Patient Continuous Monitoring"
Section 16 receives an appropriate receiver output which is applied
to a digital-to-analog converter 68. The one shown is responsive to
receiver No. 1 and processes data from patient 1. Here the
digitally coded data from a transmitter 66, and received by
Receiver No. 1, is converted to analog form and the output of each
data channel is appropriately sampled, held between samples and
filtered to reproduce the original measurements. As shown, five of
the measurements are utilized in this section, ECG-A, ECG-B, ECG-C,
arterial blood pressure D and indirect blood pressure E (which
could be used for other data). The other measurement channels F, G,
and H are available as needed for analog analysis. One of the ECG
signals, ECG-A, is applied to tachometer and meter driver 70 and
thence to counts-per-minute meter 72 for direct readout of heart
rate. Meter 72 also includes upper and lower limits which power,
respectively, upper and lower limit alarm lights 74 and 76. This
permits the preset of critical limits for a given patient as
determined by his doctor and thus provides selective critical care
for that patient. As a still further aid to the detection of a
dangerous change in heart condition, a heart signal output, such as
from ECG-A, is fed to preshock detector and alarm 78, which detects
the presence of higher than normal voltages and energizes alarm
light 79.
Continuous visual observation of any one of a particular patient's
condition as provided by any one of the outputs of
digital-to-analog converter 68 is achieved by connecting the output
to cathode-ray display 20 which has an allotted space slot for each
patient as illustrated in FIG. 4. As shown in FIG. 3, switch 80 is
arranged to selectively connect any one of outputs A-E to the
patient No. 1 input of cathode-ray display 20.
In addition to the graphical display of blood pressure, outputs D
and E of digital-to-analog converter 68, blood pressure is also
indicated on meter 81 which includes adjustable upper systolic and
lower systolic limit detection which energizes a low or high limit
alarm, lights 82 or 83 as the case may be, if a preset value is
passed. In addition, systolic detector and diastolic detectors 84
and 86 and which control meter 81 also provide an output in the
form of an electrical pulse to "decode for word" stage 88 of
patient selective monitoring section 18 indicating the time of
occurrence of upper and lower peak values of blood pressure which
indications are used to identify in time the appropriate digital
word carrying a precise value for such high or low value. The
operation of this portion of the system will be further discussed
below.
As another mode of indicating selected outputs of digital-to-analog
converter 68, recorder 90 may be connected to continuously record
any one of these outputs.
Decimal readout of physiological conditions monitored by the system
are controlled by patient control 92 responsive to patient selector
94, in Patient Selective Monitoring Section 18. For purposes of
illustration, it will be assumed that patient No. 1 is selected.
Patient control 92 then connects an output from receiver 1 to
binary to binary coded decimal (BCO) converter 96 which,
accordingly, provides as outputs D,E,G, and H decimally coded
signals to like function decimal readouts, the D output being fed
to both systolic and disastolic blood pressure readouts 98 and 100,
respectively, the E output being fed to veinal blood pressure
readout 102, the G output being fed to external temperature readout
104 and the H output being fed to internal temperature readout 106.
In addition, gating pulses, e,g and h corresponding in time to the
occurrence of like, but upper case, lettered data outputs are fed,
respectively, to gates 108, 110 and 112 to provide data bits to
decimal readouts 102, 104 and 106 only during the precise times in
which the data is accurate as determined by binary to binary coded
decimal converter 96. Precise readout of systolic and diastolic
blood pressure requires an indication not only of the time of
occurrence of an accurate bit of data, but also the time when blood
pressure corresponds to a systolic or diastolic condition.
Accordingly, "decode for word" circuit 88, a switching circuit,
receives systolic and diastolic "when" pulses from systolic
detector 84 and diastolic detector 86, respectively, and applies
same appropriately to "AND"-gates 114 and 116. Gates 114 and 116
are also provided with word readout marking pulses "d" from binary
to binary coded decimal converter 96. When coincident pulses are
applied to one of the "AND" gates a gating pulse is applied to
gates 118 or 120, as the case may be, and accurate decimal readout
of systolic or diastolic blood pressure on readouts 98 or 100
obtained. Patient selection for "decode for words" circuit 88 is
controlled by patient selector 94. Patient selector 94 also
provides for automatic cycling of the decimal readouts. This is
accomplished by selecting the "s" condition on selector 94 which
then causes the system to decimally readout in sequence data
derived from each patient. Indication of the particular patient
being observed is provided by illumination of numbers 122, a light
for a particular number being energized during the period in which
data from a corresponding patient is being read out.
The operation of this system has been generally described above.
Patient units 10 and accompanying probes are initially placed on
and with respect to each patient. Data from each patient is then
transmitted via a pulse code modulated FM link between patient
units 10 and receiving section 14 of central monitor 12. An output
from each receiver is applied to the corresponding analog section
16. The operator of the central control monitor visually scans
periodically the traces on cathode-ray display 12 corresponding to
the physiological functions of each patient. The operator
particularly selects between physiological signals to be observed
by selector switch 80. The operator also observes heart rate on
meter 72 and systolic and diastolic blood pressure on meters 81.
Dangerous blood pressure excursions are indicated by preset warning
lights 82 and 83 and a preshock condition by alarm 78. When
desired, as for example, when there is an indication of progressive
changes in a patient, particular functions may be recorded on tape
recorder 90.
The operator may also selectively observe decimal readouts for
precise determination of blood pressure, including systolic and
diastolic blood pressure, for any patient. In addition, both
external and internal temperature are made decimally available for
examination.
In summary, by means of reasonable attention and selection a single
operator is able to provide intensive and extensive observation of
a number of patients, a feat not previously possible. It is
therefore concluded that the inventors have provided a new and
novel system for more complete patient care, and with substantially
less personnel effort than heretofore possible.
* * * * *